Characterization of nickel sulphide thin films prepared by modified chemical method

Semiconducting nickel sulphide (NiS) thin films were deposited onto glass substrates using a new modified chemical bath method (MCBD). The MCBD is the solutions grow technique in which substrates are immersed in cations and anions alternatively and film growth takes place on the substrates. The preparative conditions such as concentration, pH, temperature, immersion time, immersion cycles, etc are optimized to get nanocrystalline NiS films. The characterization of the films was carried out by using X-ray diffraction, scanning electron microscopy, optical absorption and electrical resistivity. The XRD analysis of the as-grown NiS films showed hexagonal structure. The average grain size is found to be 14 nm. Electrical resistivity measurements showed semiconducting nature with at room temperature resistivity which is found to be of the order of 10 Ωcm for as-deposited NiS films. Scanning electron micrographs (SEM) reveal a very dense surface structure with the presence of irregular shaped grain particles of size ~200 nm. The optical absorption studies show that the absorption coefficient of the NiS thin film is high and a direct band gap of ~2.4 eV has been observed